Air pollution is a major global problem. Although breathing-related illness and poor air quality are a global problem, some parts of the world are particularly affected. Some of the worst air quality in the word exists in major metropolitan areas. Cities like Los Angeles, London, Mexico City, Beijing, and New Delhi are examples of major metropolitan areas with exceptionally poor air quality.
An estimated 3.2 million people died prematurely in 2010 because of the poisonous effects of outdoor air pollution, according to the findings of an exhaustive study of global causes of death published in an issue of the British medical journal Lancet. Two-thirds of those killed by air pollution lived in Asia, where air quality continues to deteriorate.
According to recent studies in the U.S., the total annual cost of providing healthcare related to all respiratory conditions, excluding lung cancer, was $113 billion. The study further estimated that the cost to American society, in terms of lost productivity as a result of disability and early death due to respiratory disease, amounted to an additional $67 billion.
The Environmental Protection Agency (EPA) groups particle pollution into two categories. Inhalable particles classified as “coarse”, such as those found near roadways and dusty industries, are between 2.5-10 micrometers in diameter. Fine particles, such as those found in smoke and haze, are smaller than 2.5 micrometers in diameter. These particles can be directly emitted from sources such as forest fires, or they can form when gases are emitted from power plants. The size of particles is directly linked to their potential for causing health problems. The EPA is concerned about particles that are smaller than 10 micrometers in diameter because those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects. Particulate matter in the air is directly linked to breathing and health problems of varying severity depending upon the time and level of exposure. The ability to remove particulate matter from the air in and around cities represents a potential saving in the tens of billions in reduced healthcare costs to the U.S. GDP.
While industrially-generated pollutants (e.g. both gaseous pollutants such as CO2, as well as particulate pollutants) can be—and are often mandated to be—remediated at the source, the majority of particulate pollution sources do not lend themselves to this means of remediation. Instead, particulate air pollution must be treated after it has been released and been diffused into the atmosphere, often a great distance from the source. This creates certain problems.
First, it is easier to remediate air pollution at the source because industrial pollutant exhaust gases can be routed through remediation means before being released into the atmosphere, i.e. before they go through the exhaust stack. However, particulate pollutants such as smoke and asphalt dust are often generated over wide areas, which does not lend itself to easy control. Particulate pollution is therefore dispersed in a huge volume of air. For example, assuming that most pollutants are contained below 30,000 ft, the volume of polluted air in a large metropolitan area with a 30 mi radius is 2.3×1015 ft3 or about 15,000 cubic miles. Being able to capture and effectively channel this huge volume of polluted air through remediation means is a major problem.
Obviously, one way to do this would be at a single remediation site. However, unless the site is of gigantic proportions, it is very unlikely that such single-site remediation is going to be effective, simply because of the vast volumes of air involved, and because of the vagaries of air current and atmospheric conditions. Moreover, building and operating such a large-scale remediation facility would be costly, which makes construction of such a facility with public funds politically challenging. The high cost of such a facility (aside from the physical plant itself) results largely from the difficulty of finding enough suitable land in the right location in metropolitan areas, where land is at a premium, and therefore expensive.
A widely-distributed method of remediating particulate air pollution is therefore a more desirable solution. Not only does such a method circumvent the difficulty in finding a suitable single site and the cost of building such a facility, but a distributed method also allows a greater volume of polluted air to be accessed and processed. However, a widely-distributed method would require a remediation means that is easily dispersible among already-existing urban infrastructure so that its installation involves the minimum of disruption to the public. Ideally, it would involve a device that can be retrofitted to existing devices that handle relatively large volumes of air. In addition, it must be a device whose use can be mandated, to ensure that its use is widespread. The success of automobile catalytic converters in reducing auto emissions is instructive. These were successful in reducing air pollution from automobiles in part because their use was mandated by law.
What is therefore needed is a method of remediating particulate air pollution that is able to be retrofitted to existing devices that move large amounts of air, inexpensive, and whose use could easily be mandated.